Technical Field
The present document is for a wireless communication system. More particularly, the present document is for a wireless communication with reduced internal signaling burden in the distributed antenna system (DAS) by applying hierarchical structure.
While the present document mainly discuss this with the example of implementing in-vehicle DAS system, it is only exemplary, and the proposed scheme/structure can be used for simple configuration of MIMO system with DAS configuration.
Discussion of the Related Art
In the conventional mobile communication system for mainly serving personal mobile communication devices, there is an inverse proportional relationship between the speed of the UE and required data rate/QoS. So, the conventional communication system is configured to provide high data rate/QoS for low speed UE, and to provide reliable service without radio link failure for the high speed UE even the data rate/QoS is somewhat low.
In the next generation communication system, there is a need for high data rate/QoS for the high speed UE, since the scope of the required service increase. For example, the users in the vehicle or public transportation would like to enjoy multi-media service during the drive through highway. Also, users want to enjoy multi-media service more while the speed of the vehicle is high.
In order to fulfil these needs, there can be two approaches. One is improving the network infra itself for high quality service to high speed users, and the other is a new system/scheme for this without affecting the network infra.
As one of the solution for the second approach, a vehicular MIMO system is considered. In conventional vehicular MIMO system, large size antenna arrays are implemented to the vehicle for this end. However, implementing the large size antenna array in the outside of vehicle has drawback for vehicle design and for aerodynamics. So, the vehicle vendors are reluctant to implement this kind of large antenna array. Presently, vendors prefer to use shark antenna system in their vehicle.
FIG. 1 shows a structure of conventional shark antenna system for vehicular communication.
The conventional shark antenna system is a combinational antenna system. As shown in FIG. 1, the shark antenna system implemented various antennas within one physical structure. In FIG. 1, the shark antenna includes combined structure for 4 or more different band/services in one antenna. So, it has limit for providing high quality mobile communication service.
However, the reason why the vendors prefer this instead of large antenna system is to reduce the space for the antennas. Large sized antennas would not good for car design and reduce the original driving performance of the vehicle.